The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the inventors hereof, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted to be prior art against the present disclosure.
In systems of the type mentioned above, the information is generally recorded in a plurality of concentric circular or spiral paths or tracks on the disk. The head that writes data to and/or reads data from the disk must follow particular ones of these tracks in order to write data to or read data from the disk.
In order to read desired information from the disk, the read head must be properly located over the track containing that desired information. To facilitate such read-head positioning, the disk is also recorded with several radially extending and angularly spaced “servo wedges” of information that contain track-identifying information, and also information that can be used to control the read-head-positioning mechanism to optimally center the read head over the desired track, especially in the direction that is radial of the disk (e.g., position error signals, or “PESs”).
Servo wedge information is typically recorded on a storage medium at the time of manufacture. One technique for recording servo wedge information is “self-servo write” (“SSW”), in which the storage device's own read/write mechanisms, including data channel controllers and read/write heads, are used to write the servo wedge information under control of an external processor. The servo patterns to be written typically are created by hard coding, or by specialized circuits or complex state machines.